Subscriptions R5 Backport
0.1.0 - ballot

Subscriptions R5 Backport, published by HL7 FHIR Infrastructure WG. This is not an authorized publication; it is the continuous build for version 0.1.0). This version is based on the current content of https://github.com/HL7/fhir-subscription-backport-ig/ and changes regularly. See the Directory of published versions

Payloads

Payload Types

There are three options available when specifying the contents of a Notification: empty, id-only, and full-resource. These options change the level of detail conveyed in the notification Bundle.

When deciding which payload type to request, systems SHOULD consider both ease of processing and security of PHI. To mitigate the risk of information leakage, systems SHOULD use the minimum level of detail consistent with the use case. In practice, id-only provides a good balance between security and performance for many real-world scenarios.

If a server will not honor a payload type (e.g., will not send full-resource over HTTP), it SHOULD reject the Subscription request, but the server MAY accept the subscription with modifications.

Empty

With the content type of empty, all information about the resources involved in triggering the notification is only available via channels other than the Subscription itself (e.g., the REST API). This mitigates many security concerns by both removing most PHI from the notification and allows servers to consolidate authorization and authentication logic. When the subscriber receives a notification of this type, it may query the server to fetch all the relevant resources based on the SubscriptionTopic and applicable filters. The client might include a _since= query parameter, supplying its last query timestamp to retrieve only the most recent resources. For example, if the notification is for a topic about patient admission, the subscriber will generally query for recent Encounters for a patient or group of patients, then fetch them as needed.

When the content type is empty, notification bundles SHALL not contain Bundle.entry elements other than the Parameters used to convey status information about the notification.

Id Only

With the content type of id-only, the resources involved in triggering the notification are only available through other channels (e.g., REST API), but notifications include URLs which can be used to access those resources. This allows servers to consolidate authorization and authentication logic, while removing the need for expensive queries by subscribers. When a subscriber receives a notification of this type, it may directly fetch all the relevant resources using the supplied resource ids. For example, the if the notification is for a topic about patient admission, the subscriber may fetch the Encounters for a patient or group of patients.

When the content type is id-only, notification bundles SHALL contain, in addition to the Parameters used to convey status information, at least one Bundle.entry for each resource relevant to the notification. For example, a notification for a topic based on Encounter SHALL include a reference to the Encounter and MAY include additional resources deemed relevant (e.g., the linked Patient).

Each Bundle.entry for id-only notification SHALL contain a relevant resource URL in the fullUrl, request, and/or response elements. The Subscription’s notificationUrlLocation element describes the behavior which should be used.

Full Resource

With the content type of full-resource, the resources involved in triggering the notification are included in the notification bundle. When a subscriber receives a notification of this type, resources are already present in the bundle, though the subscriber may need to fetch additional resources from the server. For example, the if the notification is for a topic about patient admission, the subscriber may require related Observation resources.

When the content type is full-resource, notification bundles SHALL contain, in addition to the Parameters for status information, at least one Bundle.entry for each resource relevant to the notification. For example, a notification for a topic based on Encounter SHALL include an Encounter and MAY include additional resources deemed relevant (e.g., the relevant Patient).

In most scenarios, each Bundle.entry for a full-resource notification SHALL contain a relevant resource in the resource element. In some scenarios, it is not possible to include the resource, in which case entry.request and/or entry.response are required. For example, in the case of a notification about a deleted resource, the server may no longer have access to the resource. In this case, information in the entry.response is critical for a subscriber to process the notification (e.g., the etag).